Transformation of relaxation oscillations



Feb. 14, 1939. K SCHLESINGER' 2,147,559

TRANSFORMATION OF RELAXATION OSCILLATIONS Filed Oct. 16, 1936 PatentedFeb. 14, 1939 UNITED STATES TRANSFORMATION OF RELAXATION OSCILLATIONSKurt Schlesinger, Berlin, Germany, assignor to RadioaktiengesellschaftD. S. Loewe, Berlin- Steglitz, Germany Application October 16, 1936,Serial No. 106,021 In Germany October 25, 1935 8 Claims.

The invention relates to a' relaxation oscillation generator supplyingthe deflecting voltage for a cathode ray tube.

An object of the invention is the use of a transformer coupling betweenrelaxation oscillation generator and the deflecting systems of thecathode ray tube. Such a transformer coupling in view of the lowdeflecting power of the Braun tube is able to effect a considerableincrease in the deflecting potential. The internal resistance betweenthe deflecting plates of a cathode ray tube may amount to approximately10 ohms and the deflecting power in respect of several hundred voltsdeflecting potential only amounts to a few tenths of a watt. If,therefore, approximately 10 Watts are employed on the primary side, a

\/ 10-fold potential amplification is conceivable. Amplitudes of theorder of 10 volts are accordingly sufiicient on the primary side, whichrenders possible in the case of relaxation apparatus the use of anodebatteries of low potential. I

The present invention deals with the question of a form of relaxationoscillation which is devoid of error. It is not a readily possiblematter to transmit a relaxation oscillation true to form by way of atransformer.

Fig. 1 shows a conventional circuit arrangement for coupling arelaxation oscillator amplifier to an inductive load.

Figs. 2 and 3 show' arrangements embodying the invention. I

In the drawing Figs. 2 and 3 show" arrangements for performing theinvention. In Fig. 1 the end stage I is connected at the grid with arelaxation oscillation generator 2. It possesses an internal resistance3 (Bl). The transformer 4 possesses an impedance composed of ohmicresistance 5 and inductive reactance 6. If it were possible to apply tothe primary terminal of the transformer .an undistorted relaxationpotential of the form of curve of the generator 2, a transformation trueto form would'be capable'of being performed. The secondary potentialwould have the value e,-Ma (1) and the current would have a form ofcurve differing greatly to the relaxation curve. The integral curve ofthe primary potential would be operation of the amplifier. It is only tobe obtained when the apparent resistance of the transformer is verylarge as compared with the internal resistance of the tube. By the useof tubes without screening grids, i. e., of 3-electrode tubes with largereciprocal of the amplification factor andlarge steepness, that is tosayfismall internal resistance, the condition of idle operation may bevery closely approached. Actual accomplishment of idle operation isimpossible in practice, as it is difiicult to make the transformers solarge that they operate solely with potential excitation and with verysmall primary current.

The subject matter of the inventon is a circuit which suppliesappreciable relaxation oscillations even in the case of smallcurrent-excited transformers. In this circuit the potential excitationof the relaxation apparatus itself is distorted in the manner accordingto the invention (see below), whereby the transformer distortion iscompensated. The power amplifier I, in accordance with the invention, isalready excited in a distorted relaxation curve.

By Way of explanation there is taken the extreme case of a smalltransformer, the apparent resistance 5 (Ra) of which is small ascompared wlth the internal resistance (Ri) of the tube l. Thetransformer then operates in a current-confining tube, which by way ofthe same is apparently shcrt-circuited (case of shortcircuit). In thiscase the current it is an undistorted relaxation curve, and according toFormula (l) the transformer provides on the secondary side thedifferential curve of the primary current curve, which is unsuitable fortelevision purposes.

Actually the state of operation is always something in between idleoperation and short-circuit. The terminal potential of the transformerthen consists of a purely ohmic and an inductive component. There isaccordingly connected with the anode of the amplifying tube I apotential according to the following Equation (3) According to Formula(1), the secondary popose of being able to derive a clean relaxationcurve from the secondary of the transformer.

The Formula (4) supplies the condition for the form of curve of the gridalternating potential with which the amplifier requires to be excited.It Will be seen that this grid alternating potential may not have a purerelaxation curve form. It is not sufiicient to add the expression B't.This would merely suffice for no-load operation. The short-circuit valueA-f must also be included, and it must be added in a ratio to theundistorted grid potential which is determined by the circuit. Theshort-circuit value, according to Equation (i), is the integral of therelaxation oscillation. According to the invention, the grid excitationof the power amplifier I is composed of an undistorted relaxationpotential curve and a superposed integral of this relaxation potentialcurve.

Fig. 2 shows a circuit which enables the Equation (4) to be fulfilled inpractice. The second integration of the relaxation curve is effected inthis circuit by charging a condenser. An anode battery I charges a firstcondenser 9 by way of a resistance 8. This charging takes place withconstant current so long as the charging potential at 9 remains small ascompared with the mains potential I. If, for example, the resistance 8is made=l00,000 ohms and the condenser 9:1;if, the maximum potential at9 in the case of a relaxation frequency of 25 cycles per second will be30% of 7, and the time curve of the charging potential of the condensermay be regarded in first approach as linear curve. There are accordinglyobtained at 300 volts mains potential relaxation oscillations ofapproximately 100 volts amplitude and linear form. (Naturally a stillbetter linearity may be obtained by not allowing the con.- denserpotential to become quite so high.) The integration at this undistortedrelaxation curve called for by the Equation l) is performed by the factthat a second resistance I charges a second charging condenser II. Theresistance III is made approximately ten times greater than theresistance 8, whilst the time constant of the circuit comprisingresistance In and condenser Ii, of the so-called integration circuit, isselected to be, with the same requirements for linearity, just as greatas the time constant of the first circuit comprising resistance 8 andcondenser E. There may accordingly be selected, for example: resistance3:10 ohms, condenser II=0.l f. In this case the current flowing in theintegration circuit is neglegible for the primary circuit 8/3. Thepotential at the condenser II increases parabolically when the potentialat the condenser 9 increases in linear fashion. By displacement of atapping I2 over the resistance It] a suitable fraction of the twocondenser potentials 9 and I I may be adjusted and conducted tothecontrol grid of the tube I. The tube I is then so strongly negativelybiased, preferably by the battery I3, that it operates without gridcurrent. The anode circuit of the tube is connected with the relaxationtransformer 4. In specific instances it is very important to constructthe transformer 4 as push-pull transformer. This instance exists in thecase of high-vacuum tubes with simple and with double electrostaticdeflection. The pushpull operation ensures constant sharpness of theimage point at the edge of the image. It may also be of advantage tomake the insulation between the primary winding 4a and the secondarywinding 41) of the transformer 4 proof against high tension. The innercore of the transformer should be so dimensioned that saturation by theemissive current of 1 is avoided. It is naturally also possible byemploying two power amplifier stages I already to perform push-pulloperation on theprimary side and in this way to avoid saturation of thetransformer iron core.

The discharge of the condensers 9 and H may be effected by means of adischarge tube I2, which in the condition of charge is blocked bynegative bias I4 and is 'made conductive by the synchronisationimpulses. There may also be employed two discharge tubes I2 and I2a foreach of the two condensers 9 and II, the grid of which may be connectedin parallel. When operations are performed with one single dischargetube I2 a bridging condenser I5 may be useful, which is so small that itdoes not aifect the charging operation but upon the discharge causes amore rapid discharge of the condenser II and accordingly an improvementin the return speed. In the present case I5 might amount toapproximately 0.01m.

In-place of high-vacuum discharge tubes I2 there may also be employedwith advantage gasfilled hot cathode tubes, which have the property ofigniting and thus discharging automatically after a maximum potential,which is adjustable by their grid, has been reached.

In Fig. 2 the integral circuit comprising resistance I0 and condenser II is connected directly with the first charging circuit comprisingresistance 8 and condenser 9. Naturally the potential distortionaccording to the invention in accordance with Equation (4) may also beperformed in separate circuits and subsequently added together. a

In Fig. 3 there is shown a circuit diagram of this kind, in which thecharging circuit comprising resistance 8 and condenser 9 is separatedfrom the integral circuit comprising resistance I0 and condenser II by atube l5. The tube I5 receives its anode potential by way of a potentialresistance I6, which is small in relation to the resistance I0. By meansof a potentiometer Ifla a mixing of the potential of the two condensersmay be performed in desired ratio with the aid of a sliding contact I2,and this mixture in accordance with Equation (4) passed to the end tubeI and the transformer 4. Numerous other circuits are also possible,which make use of the method of integration of the undistortedrelaxation curve according to the invention.

In a practical embodiment of Fig. 2 with an RE134- as output valve it.was possibleto perform push-pull transformation 1' to 10, in which itwas successful in obtaining an exact image point with 400 voltsrelaxation amplitude by the use of an anode battery 1 of merely 300volts and with an anode current of merely 5 ma. The power requirementfor this relaxation apparatus, which operated with .a gas-filled gridcontrolled discharge tube I2, accordingly amounted to only 1.5 W. Incomparison therewith constructions without relaxation transformationwith resistance amplification at 1,000 volts anode potential required20-30 ma., i. e., more than ten times the stated power.

I claim: I V

1. An arrangement for producing deflecting voltages of saw-tooth 'waveform for deflecting the cathode ray in a cathode ray tube comprising arelaxation'oscillation generator having input and output terminals, atransformer having a primary and a secondary winding, means forintegrating the potential occurring at said output terminals, means forsuperimposing said integrated potential on said output potential andmeans for applying said superimposed potentials to said primary winding,said secondary Winding being connected to the deflecting system of saidcathode ray tube.

2. An arrangement for producing deflecting voltages of saw-tooth waveform for deflecting the cathode ray in a cathode ray tube comprising arelaxation oscillation generator having input and output terminals, anelectronic amplifier, a transformer having a primary and a secondarywinding, means for integrating the potential occurring at said outputterminals, means for superimposing said integrated potential on saidoutput potential and means for applying said superimposed potentials tothe input of said electronic amplifier, the output of said electronicamplifier being connected to said primary Winding, said secondarywinding being connected to the deflecting system of saidcathode raytube.

3. An arrangement for producing deflecting voltages of saw-tooth waveform for deflecting the cathode ray in a cathode ray tube comprising arelaxation oscillation generator having input and output terminals, anelectronic amplifier, a transformer having a primary and a secondarywinding, a resistance and a condenser, the potential occurring at saidoutput terminals being supplied through said resistance to saidcondenser, means for superimposing the potential formed on saidcondenser on said output potential and means for applying saidsuperimposed potentials to the input of said electronic amplifier, theoutput of said electronic amplifier being connected to said primarywinding, said secondary winding being connected to the deflecting systemof said cathode ray tube.

l. An arrangement for producing deflecting voltages of saw-tooth waveform for deflecting the cathode ray in a cathode ray tube comprising arelaxation oscillation generator having input and output terminals, anelectronic amplifier, a transformer having a primary and a secondarywinding, a potentiometer resistance, a tapping point on saidpotentiometer resistance and a condenser, the potential occurring atsaid output terminals being applied through said potentiometerresistance to said condenser, the tapping point of said potentiometerresistance being connected to the input circuit of said electronicamplifier, the output of said electronic amplifier being connected tosaid primary winding, said secondary winding being connected to thedeflecting system of said cathode ray tube.

5. An arrangement for producing deflecting voltages of saw-tooth waveform for deflecting the cathode ray in a cathode ray tube comprising arelaxation oscillation generator including a charging condenser and agrid-controlled high vacuum discharge tube, an electronic amplifier, atransformer having a primary and a secondary winding, a potentiometerresistance, a tapping point on said potentiometer resistance, a secondcondenser and a second grid controlled high vacuum discharge tube fordischarging said second condenser, the potential occurring at theterminals of said first charging condenser being applied through saidpotentiometer resistance to said second condenser, the tapping point ofsaid potentiometer resistance being connected to the input circuit ofsaid electronic amplifier, the output of said electronic amplifier beingconnected to said primary winding, said secondary Winding beingconnected to the deflecting system of said cathode ray tube.

6. An arrangement for producing deflecting voltages of saw-tooth waveform for deflecting the cathode ray in a cathode ray tube comprising arelaxation oscillation generator including a charging condenser and agrid controlled gasfilled discharge tube, an electronic amplifier, atransformer having a primary and a secondary Winding, a potentiometerresistance, a tapping point on said potentiometer resistance, a. secondcondenser and a second grid controlled gas-filled discharge tube fordischarging said second condenser, the potential occurring at theterminals of said first charging condenser being applied through saidpotentiometer resistance to said second condenser, the tapping point ofsaid potentiometer resistance being connected to the input circuit ofsaid electronic amplifiers, the output of said electronic amplifierbeing connected to said primary Winding, said secondary winding beingconnected to the deflecting system of said cathode ray tube.

7. An arrangement for producing deflecting voltages of saw-tooth waveform for deflecting the cathode ray in a cathode ray tube comprising arelaxation oscillation generator including a charging condenser and agrid-controlled high vacuum discharge tube, an electronic amplifier, atransformer having a primary and a secondary winding, a potentiometerresistance, a tapping point on said potentiometer resistance, a secondcondenser and means for discharging said second condenser through saiddischarge tube of said first condenser, the potential occurring at theterminals of said first charging condenser being applied through saidpotentiometer resistance to said second condenser, the tapping point ofsaid potentiometer resistance being connected to the input circuit ofsaid electronic amplifier, the output of said electronic amplifier beingconnected to said primary winding, said secondary winding beingconnected to the deflecting system of said cathode ray tube.

8. An arrangement for producing deflecting voltages of saw-tooth waveform for deflecting the cathode ray in a cathode ray tube comprising arelaxation oscillation generator including a charging condenser and agrid controlled gasfilled discharge tube, an electronic amplifier, atransformer having a primary and a secondary winding, a potentiometerresistance, a tapping point on said potentiometer resistance, a secondcondenser and means for discharging said second condenser through saiddischarge tube of said first condenser, the potential occurring at theterminals of said first charging condenser being applied through saidpotentiometer resistance to said second condenser, the tapping point ofsaid potentiometer resistance being connected to the input circuit ofsaid electronic amplifier, the output of said electronic amplifier beingconnected to said primary Winding, said secondary Winding beingconnected to the deflecting system of said cathode ray tube.

KURT SCHLESINGER.

